This invention relates to plastic pigments for paper coatings having excellent opacity, visual gloss and improved pick resistance.
Most paper surfaces require a coating in order to have good printing qualities and adequate opacity. Conventional paper coatings contain inorganic pigments such as kaolin clay or titanium dioxide to impart the required opacity to the coated paper substrate. However, the inorganic pigments substantially increase the coating weight thereby increasing mailing costs. Inorganic pigments also tend to lower coating gloss and pick resistance.
Recently, paper coatings containing discrete plastic particles as pigment have been disclosed in U.S. Pat. No. 3,779,800 to E. Heiser and U.S. Pat. No. 3,595,823 to D. Huang. While coating weight is lower and gloss is generally improved in such coatings, the pick resistance of such coatings is not appreciably improved over that of the inorganic pigment coatings. Further, paper coatings containing the plastic pigment exhibit increased tendency to stick to calender rolls during the finishing process.
Accordingly, it would therefore be highly desirable to provide a paper coating having improved pick resistance and resistance to sticking during calendering while retaining other characteristics similar to those of the aforementioned U.S. Pat. No.